The field of epidemiology studies the health of populations with any eye to detection and prevention of illness.

Disease is fascinating in any light, and as our world shrinks due to global travel we’re likely to see a lot more of it in new guises. Single cases of disease in exotic places are a potent threat to major population centres, because that single person can travel round the world in a single day.

Securing yourself against infection is a proper arms race: infectious agents and defences improving in lock-step, forever exploiting and then being beaten back.

Nothing about the above paragraphs is unique to biology. In the early hours of the 25 January 2003 the fastest-spreading global infection ever seen first began to take hold, on the internet.

The infection, known as the Slammer worm, was the first of a new kind of Warhol worm — one that would spread as fast as it could within its “15 minutes of fame”. This epidemiological analysis of the appearance, spread and weaknesses of the Slammer worm make fascinating reading for the geeky. ( This is what happened. )

There’s a world of stupid reasons why programs crash and there’s an equally big list of ways in which bad code can lead to security flaws. And because I thought it would be interesting (for me, at least) I thought I would write about them.

Today’s flaw of choice has the foxy name of the SQL injection attack. It pops up wherever a database is used to store information — most often in complex web sites.